The use of casters to facilitate the movement of equipment, for example, on adjustable beds for use in long-term care facilities or hospitals, is known. An typical adjustable bed includes a frame supported by legs. In a conventional adjustable bed, movement of the legs causes movement of the frame relative to a floor surface supporting the bed. The frame holds a mattress support on which a mattress is placed. Typical adjustable beds are disclosed in U.S. Pat. No. 4,097,939 (Peck et al.) and U.S. Pat. No. 6,230,344 (Thompson et al.).
The conventional adjustable bed extends between a head end and a foot end, and the legs extending towards the floor surface at the head end are typically supported above the floor surface by casters or rollers. For example, Thompson at al. discloses an adjustable bed in which the legs at the head end are supported by rollers. In known adjustable beds, the legs extending towards the floor surface at the foot end are often supported above the floor surface by feet, as disclosed in Thompson et al. However, it is also known that the legs extending towards the floor surface at the foot end may be supported by casters, as disclosed in Peck et al. Movement of the legs (i.e., to cause movement of the frame relative to the floor) can be cooperative or independent in known beds.
Substantially vertical movement of the frame (i.e., substantially straight up or down) is often required. In known adjustable beds, however, substantially vertical movement of the frame relative to the floor surface is accompanied by horizontal movement of the supporting legs at the casters or rollers, as the case may be, which support the legs on the floor surface. This is shown in FIG. 1, which is a side view of a prior art adjustable bed 30. (As will be described, the remainder of the drawings illustrate the present invention.)
As seen in FIG. 1, the prior art adjustable bed 30 includes a frame 31, and the adjustable bed 30 also has a head end 32 and a foot end 33. It will be understood that the other side (not shown) of the prior art adjustable bed is the same in all material respects as the side thereof shown in FIG. 1. The frame 31 is supported by legs 34, 35 which are supported on a floor surface 36 by rollers 37 and feet 38 respectively. Legs 34, 35 are moved in order to effect generally upward or downward movement of the frame 31 relative to the floor surface 36.
As indicated in FIG. 1, when the frame 31 is moved substantially downwardly, the rollers 37 are forced to move horizontally along the floor surface 36 to a position indicated at X. Because the legs 36 are supported on the floor surface 36 by feet 38, no horizontal movement takes place at the foot end 33.
In known adjustable beds, the horizontal movement of the casters or rollers on the floor surface resulting from vertical movement of the frame tends to result in simultaneous limited horizontal movement of the frame as well, as is well known in the art. For example, in paragraph 39 of U.S. Published Patent Application No. US2001/0047547 A1 (Paul), reference is made to horizontal movement of a bed frame resulting from, and simultaneously with, vertical movement of the frame.
It is desirable to minimize the floor area required for the operation of an adjustable bed (i.e., the “footprint”). The smaller the adjustable bed footprint, the larger the patient capacity of a health care facility. However, in known adjustable beds, the footprint tends to be larger than the bed frame due to horizontal movement of the frame during its vertical movement.
Directional locks for maintaining a wheel assembly of a caster in a predetermined position are known. A directional lock can be used, for example, for maintaining the wheel assembly of the caster in a position as the caster wheel rotates. Known directional locks are disclosed in U.S. Pat. No. 5,242,035 (Lange), U.S. Pat. No. 5,303,450 (Lange), U.S. Pat. No. 5,653,096 (Edwards), U.S. Pat. No. 6,240,713 (Thomas), and U.S. Pat. No. 6,321,878 (Mobley et al.). However, known directional locks typically include a mechanism inside a caster housing for controlling the direction of travel of the wheel assembly, so that the known directional locks are usually somewhat complex and relatively expensive.
Edwards discloses “a simple hand operated locking pin” which can be inserted into a caster wheel frame to lock the caster (col. 2, lines 36-39). However, in Edwards, the caster is required to be positioned to receive the locking pin before the locking pin can be moved by a user to engage with the caster.
There is therefore a need for an improved directional lock for a caster and, more particularly, an improved directional lock for a caster on an adjustable bed.